Bilfer Pit in Apjdes. :?! 



staiuliiig is distinctly brosvn, darkens \vitli Fc Cl.j. and shows a faint 

 pinkish shinnner against the brown with solid KCN. With an excess 

 of alcohol and etlier a flocculent brown pj-ecipitate is foi-niLMl. 

 soluble in water, and consisting largi'ly of glucose, but Ijlackcning 

 with Fe ('\.^ and showing brown with a pinkish shimmer with 

 KCN. 



If the slowly expressed sap is boiled before filtering, the filtrate 

 remains almost colourless in air, but turns brown with NaHO, pink 

 with KCN, disappearing and reappearing on shaking and stand- 

 ing, and green darkening to a <listiiict tannic acid reaction with 

 Fe CI3. The residue on the filter paper contains less tannic acid. 

 Apparently some of the tannic acid present in the slowly expressed 

 sap is not present in the natural sap, but is taken up from the 

 protoplasm after the latter has been killed. The non-browning of 

 the sap from boiled pulp suggests the presence of an oxidase enzyme 

 destroyed by heat. 



J. af Klercker (Bihang till d. Svenska Vet. Ak. Handl. Bd. xiii. 

 111. 1888), concluded that tannin might eithei- occur in the cell 

 sap or in tlie protoplasm in the form of oil-like drops formed 

 by the fusion of smaller ones, but that the actual substance of the 

 protoplasm was always free from tannin. To test this apples 

 peeled on one side (Plate V.) were immersed in solutions of ferric 

 ■chloride, and of methyl blue and the coloured pulp examined after 

 «ome days. With Fe CI5 the walls of the pulp cells remained prac- 

 tically colourless, and also the vacuole, whereas the protoplasmic 

 ■contents turned brown. Under high powers round or occasion- 

 ally oval vesicles of tannic acid stained brown with Fe CI.;, and 

 dark blue with methyl blue, could be distinguished readily in rhe 

 protoplasm of the pulp cells. Apparently the Fe Cl.j causes a slight 

 contraction in size of the vacuoles, but in very many cells they are 

 extremely abundant and conspicuous, and none of the pulp cells 

 appear to be entirely free from them. If these tannic acid vacuoles 

 •exist in the living protoplasm, they would constitute a second osmotic 

 system, each vacuole being surrounded by either a precipitation 

 membrane or an organised plasmatic membrane, so that tannic acid 

 could only escape from them when the osmotic membrane was 

 destroyed and no new one formed. 



T//r iia flirt- 0/ f/w fdiniiii iiuitcrinl. 



From its relative solubilities in alcohol and in ether, it may be 

 •concluded that it occurs in the form of tannic acid and not of trallic 

 iicid. Nevei-theless, on boiling acid ])u1i) some of the tannic ;uid 



